DECHEMA

About: DECHEMA is a nonprofit organization based out in Frankfurt am Main, Germany. It is known for research contribution in the topics: Corrosion & Oxide. The organization has 756 authors who have published 1307 publications receiving 25693 citations.

Novel corrosion protective coatings for aluminium alloys and steels based on oxidic nanoparticles

Abstract: Based on chemical nanotechnology glass-like protective coatings thermally processed at comparatively low temperatures of around 500 °C were developed for aluminium and steel substrates by two different means. Starting from polymeric sols containing a multicomponent oxide of the SiO2 – B2O3 – P2O5 – Na2O system produced by sol-gel technology under acidic conditions, coatings were developed which are thin, hard, transparent, crack-free and corrosion resistant. Electrophoretic deposition of coatings from particulate sols containing multicomponent oxide synthesised under basic conditions proved to be a promising method when very thick coatings are required. Both routes offer the potential of a new type of purely inorganic coatings for corrosion and abrasion protection.

Kinetic and Thermodynamic Analysis of Hydrogen Evolution at Nickel Electrodes.

Abstract: iR-corrected steady-state polarization curves for hydrogen evolution in alkaline solution at crystalline and amorphous nickel electrodes were measured at different temperatures, showing at higher c.d. the establishment of a limiting c.d. due to increasing Had coverage. The experimental behaviour is in perfect agreement with a complete kinetic model based on the Volmer—Tafel mechanisms. Symmetry factors and rate constants for forward and backward direction of both reactions were determined by a non-linear fitting procedure. Activation energies, enthalpic and entropic components of the symmetry factor, and thermodynamic quantities as equilibrium constant of the Tafel reaction, equilibrium potential of the Volmer reaction, enthalpy and entropy of adsorbed hydrogen atoms could be derived from these data providing new quantitative knowledge of elementary steps of hydrogen evolution at crystalline and amorphous nickel electrodes.

A New Concept of an Electrochemical Heat Pump System: Theoretical Consideration and Experimental Results

Abstract: A new concept of an electrochemical heat pump system is described which consists of two identical electrochemical cells operating at different temperatures in opposite directions. The principle is based on the exchange of reversible heat (TΔRS) of the reaction. The thermodynamics and efficiency of such a system are considered for different cell reactions. Calori-metric measurements, using commercial accumulators and non-commercial redox cells, were carried out to prove the validity of the theoretical predictions with respect to heat exchange and efficiency. The efficiency of a heat pump with the redox system Cu/CuSO4//Na3[Fe(CN)6], Na4[Fe(CN)6]/Pt was found to be comparable to that of conventional heat pump systems.

Measurement of number and physiological activity of cells or organisms

Abstract: In a system for measuring the number and physiological activity of cells or organisms, esp. microorganisms, an electrical measuring signals is produced directly by redox reactions of the energy exchange of the cells or organisms.

Ultrasound Enhanced Friction Stir Welding (USE-FSW) of Hybrid Aluminum/Steel Joints

Abstract: Ultrasound Enhanced Friction Stir Welding (USE-FSW) is an innovative hybrid method for solid-state joining. This process resulted in remarkably positive findings in the successful realization of hybrid aluminum/magnesium joints as well as in first investigations on the microstructure of aluminum/steel joints due to the parallel and synchronous transmission of power ultrasound into one of the joining partners. The present work investigates the impact of additional power ultrasound on the mechanical properties of AA6061/SAE1006-joints by comparing FSW and USE-FSW. Therefore, light microscopy, as well as scanning electron microscopy, was carried out for examining the microstructure of the joints. Furthermore, mechanical tests on the microhardness of the weld zone of the joints as well as tensile and first fatigue tests were examined. The investigations proved an influence of the power ultrasound by a change in the morphology of the nugget. It showed to be more cleared up and also contains a thinner intermetallic phase of FeAl3 at the interface aluminum to steel. Furthermore, an increase in the tensile strength of the joints of about 15% could be observed. First stepwise load increase tests resulted in slightly different stress levels for the estimated fatigue limit.